Class A albedometer 3S-TP-ALBEDO-A

for weather stationsspectrally flatfor photovoltaic systems

Overview
The 3S-TP-ALBEDO-A Thermopile Albedometer measures both incoming solar irradiance and surface-reflected irradiance using two Class A thermopile pyranometers (upward and downward). It delivers accurate albedo values for PV performance monitoring, meteorological stations and solar resource assessment. The unit supports RS485 Modbus RTU integration and is built for harsh outdoor environments with IP68 protection and anodized aluminum housing, complying with ISO 9060:2018 and IEC 61724-1:2021 Class A requirements.

Key features

• Class A performance with two SEVEN 3S-TP-MB-A thermopile pyranometers (ISO 9060:2018 Fast Response, Spectrally Flat).
• Simultaneous measurement of incident and reflected irradiance for accurate albedo determination.
• Fast response time: 0.5 s.
• Low zero offset and high long-term stability.
• Digital output via RS485 Modbus RTU (optional Modbus TCP/IP).
• Robust outdoor design: IP68, anodized aluminum housing, UV- and weather-resistant cable.
• Galvanic isolation: 1000 V between power supply and RS485 bus.
• Standard 3 m cable; custom lengths available.
• 5-year warranty.

Measured parameters

• Global Horizontal Irradiance (GHI)
• Plane of Array Irradiance (POA)
• Reflected irradiance from ground, roof, snow, soil, vegetation or PV surface
• Internal temperature
• Housing temperature
• Internal humidity

Applications

• Utility-scale solar power plants
• Bi-facial PV system monitoring
• Solar resource assessment stations
• Meteorological measurement stations
• Ground reflectance and albedo studies
• Agricultural solar monitoring
• Snow, desert, roof and soil reflectance measurements
• Performance ratio and energy loss analysis in PV plants

How it works
The instrument uses two pyranometers mounted opposite each other: the upper sensor measures incoming solar irradiance and the lower measures surface-reflected irradiance. Albedo is calculated as Reflected Irradiance / Global Irradiance (example: 250 W/m² reflected ÷ 1000 W/m² global = 0.25).

Installation recommendations

• Place the unit where the upper pyranometer has an unobstructed sky view and the lower sensor represents the surface of interest.
• Avoid nearby structures or components causing shadows or reflections.
• Mount on the bracket, level using the built-in bubble level, and secure the mounting rod.
• Connect power (12–30 V DC) and RS485 Modbus RTU to the data logger or SCADA system.
• Configure Modbus parameters to match the data logger or monitoring system.

Maintenance

• Daily/field check: inspect for damage, heavy soiling, snow or bird droppings.
• Weekly: clean top and bottom domes if contaminated.
• Monthly: verify leveling, mounting integrity, cable condition and data output.
• Annual: review measurement performance and overall installation.
• Recalibration: recommended every 2 years for PV monitoring per IEC 61724-1:2021; SEVEN indicates recalibration every 5 years may be acceptable depending on application.

Warranty and options
Five-year warranty. Optional configurations with different pyranometer classes available (SEVEN 3S-TP-MB-B or 3S-TP-MB-C).

Technical specifications

• Item Code: 3S-TP-ALBEDO-A
• Measured Parameters: GHI or POA irradiance, reflected irradiance, internal and housing temperature, internal humidity
• Sensor Type: Thermopile
• Spectral Range: 280 to 3000 nm
• Irradiance Range: 0 to 4000 W/m²
• Nominal Sensitivity: 8 to 14 µV/(W/m²)
• Response Time: 0.5 s
• Zero Offset A – Thermal Radiation: ±1 W/m²
• Zero Offset B – Temperature Change: ±1.5 W/m²
• Total Zero Offset C: ±3 W/m²
• Non-Stability: <0.5% change/year
• Non-Linearity: ±0.2% from 100 to 1000 W/m²
• Directional Response: ±10 W/m² at 1000 W/m², 0 to 80°
• Spectral Error: ±0.2%
• Temperature Response: ±0.4% from -20°C to 50°C
• Irradiance Resolution: 0.1 W/m²
• Internal Humidity Range: 0% to 100%
• Internal Humidity Accuracy: ±1% RH from 20% to 70% at 25°C
• Internal Temperature Range: -40°C to +85°C
• Internal Temperature Accuracy: ±0.1°C from 5°C to 60°C
• Housing Temperature Range: -40°C to +85°C
• Housing Temperature Accuracy: ±0.2°C
• Spirit Level Accuracy: ±0.1°
• Viewing Angle: 2π sr
• Data Output: RS485 up to 38400 baud
• Communication Protocol: Modbus RTU, optional Modbus TCP/IP
• Output Rate: 1/s
• Operating Temperature: -40°C to 85°C
• Power Supply: 12 to 30 V DC
• Power Consumption: 20 mA at 24 V DC
• Cable Features: 3x2x0.14 mm², 26 AWG LI2Y(st)CTP PUR cable, UV and weather resistant
• Standard Cable Length: 3 m, custom length available
• Galvanic Isolation: 1000 V between power supply and RS485 bus
• IP Rating: IP68
• Dimensions: Ø140 mm x 209 mm
• Sensor Housing Material: Anodized aluminum
• Mounting Bracket Material: Alloy aluminum
• Shade Disk Material: ABS
• Weight: 2.6 kg
• Standards: ISO 9060:2018; IEC 61724-1:2021 Class A; ISO/TR 9901:1990; ISO 9847
• Origin: Türkiye